A. M. Kuzmitski

Compressive plasma flows interaction with steel surface: structure and mechanical properties of modified layer

The interaction of a dense compressive nitrogen plasma flow with carbon steel specimens has been investigated. The flows were generated by a magnetoplasma compressor, in which the acceleration of a plasma is accompanied by its compression due to interaction between the longitudinal constituent of electric current and the intrinsic azimuth magnetic field. As a result, a layered structure with a total depth of up to 25 μm is formed at a specimen surface. Investigations of a surface structure and its phase composition were carried out using X-ray diffraction, Mossbauer conversion electronic spectroscopy, and optical microscopy methods, along with the studies of mechanical properties.

Erosion of materials under the effect of compression plasma flows

Erosion of the surface of St3-type steel and BrB2-type bronze samples as well as bronze and copper samples with zirconium coating under the effect of compression plasma flows is studied. The results show the increase in mass removed from the surface of samples with the growth of energy absorbed by the surface layer and with the growth of the number of pulses. Probable mechanisms of erosion have been discussed. Erosion leads to the decrease in the coating element concentration in the alloyed layer in the case of the coating/substrate system treatment. This effect depends on thermal characteristics of the treated material.

Thermal stability of silicon photovoltaic structures produced using compression plasma flows

Thermal stability investigations of photovoltaic structures synthesized by the compression-plasma-flow treatment of doped silicon are performed. The samples are annealed in an atmosphere of nitrogen, in air or in vacuum in a temperature range of 100–900°C for 30 min or 3 h. The photovoltaic effect does not change after annealing at temperatures up to 600–700°C. It decreases 1.3–1.7 times after thermal annealing at a temperature of 900°C. The structure-phase changes of silicon treated with compression plasma flows are studied using X-ray diffraction and scanning electron microscopy methods. It is established that a recrystallized pre-surface layer with a thickness of 10–20 μm and modified (but not melted) layer with a thickness of up to 50–60 μm localized below the recrystallized layer are formed.

Thermal Stability of the Structure and Phase Composition of Titanium Treated with Compression Plasma Flows

The results of studying the structure and phase composition of the surface layer of commercial pure VT1-0 titanium treated with compression plasma flows in nitrogen atmosphere and annealed in the temperature range of 400–900°C for 1 h are presented. Using the X-ray diffraction method, the α-Ti(O) solid solution is found to form in the titanium surface layer at 500°C, without pretreatment with plasma, and to transform into the titanium oxide TiO2 (rutile) phase at 600°C. Pretreatment of titanium with compression plasma flows promotes the formation of α-Ti(N) solid solution decreasing the rate of surface oxidation and increasing the initial temperature of rutile formation to 700°C, which indicates enhancement of the thermal stability of this structure.

NANO-SIZED SPHERICAL CLUSTERS OF TANTALUM SILICIDE FORMED BY COMPRESSION PLASMA FLOW

A pre-deposited tantalum thin film on a Si(100) substrate was treated by compression pulsed plasma flow. SEM images demonstrated the formation of spherical clusters with multi-level structures. Formation of crystalline metal rich tantalum silicides is confirmed by X-ray diffraction and EDX elemental map analysis. The results show great potential application of compression plasma flow for the development of novel nanostructured metal-silicide materials.